A water heater or the like for household use is provided with an apparatus that detects carbon monoxide generated when incomplete combustion occurs and notifies the risk thereof at an early stage. Such a gas component considerably affects a human body. According to the guidelines from LP gas safety committee, it is set that a carbon monoxide concentration of approximately 200 ppm (parts per million) causes headaches. Although various methods have been known as a method of detecting a gas component having a relatively higher concentration, the detection methods have been limited for detecting the gas component having a concentration in the order of ppb (parts per billion) to ppt (parts per trillion), which corresponds to an extremely low concentration.
At a disaster site or a site at which an act of terrorism occurs or the like, it has been desired to sense the risk in advance by detecting an extremely small amount of the gas component. The gas component having an extremely low concentration is often detected by use of large equipment in research facilities. In this case, a large sized installation type apparatus, which is expensive and has large weight and volume, such as a gas chromatography or a mass spectrometer, is required. Under such circumstances, it has been required to provide an apparatus that is capable of detecting the gas component having the extremely low concentration in real time, in other words, an apparatus that has smaller weight and volume and better portability and enables selective and higher sensitive detection of the gas component having the extremely low concentration in the order of ppt to ppb.
Incidentally, as the gas component required to be detected at the extremely low concentration, an explosive component released from explosives used in the act of terrorism can be cited, for example. The explosives release a slight amount of explosive component even in a sealed state, it is general, on a site such as an airport or the like, to find such an explosive component by a trained police dog or the like. Though such a method is highly effective from a standpoint of deterrence, an approach by use of an animal is costly and, in addition, has difficulty in securing a constant accuracy. Other than the explosives, cyanide, which is comparatively easily available, is imagined to be gasified and used. The cyanide is used in a process of abstracting metal by treatment of a mineral as well as in a plating process or the like, comparatively easily available and having quite high toxicity, and it is said that exposure to its vapor having a concentration of about several ppm influences a human life. Thus, it is desired that a cyan-based gas (a volatile component gas or a cracked gas of cyanide) is detected at a lowest possible concentration for the sake of speedy evacuation, for a highly public facility such as a station or an airport, for example.
As a detection element for a gas component having a low concentration, for example, an element has been known which has a conductive layer in which a surface of a carbon nanostructure or graphene is surface modified with an organic substance or the like that selectively reacts with or adsorbs a specific substance and measures a potential difference or the like that changes depending on the gas component having adhered to the surface of a conductive layer. With regard to the detection element as above, the kinds themselves of the organic substance that functions as a detection probe are limited, and an organic substance enabling a sufficient interaction with a cyan-based gas (a volatile component gas or a cracked gas of the cyanide) has not been found. Under the circumstances, there are strongly demanded a molecular detection apparatus and a molecular detection method which enable detection of a cyan-based gas at a lowest possible concentration and which serve as an alternative to a method which has difficulty in securing a constant accuracy, such as a detection method using an animal.